Synthesis, characterization, and FRET interaction of pyrene-tagged β-hydroxy acid and perylen-3-ylmethylmethacrylate co-N-dodecylmethacrylamide polymer are described. The fluorescent donor, β-hydroxy acid-pyrene boronic ester was synthesized from commercially available alkyl ketene dimer via subsequent hydrolysis, reduction and esterification providing the donor. Conversely, the fluorescent acceptor was synthesized by co-polymerization of N-dodecylmethacryamide and perylen-3-ylmethylmethacrylate, where the latter was prepared from commercially available perylene in three steps. FRET interaction between the donor and acceptor was carried out by titration and monitored using fluorescence spectroscopy. Fluorescence quenching and enhancement in both film and solution formats were observed; furthermore, a more prominent lipophilic-induced interaction was observed in solution. Fluorescence enhancement (at 460 nm) is higher for the acceptor and quenching efficiency (at 420 nm) is higher for donor-acceptor pair, pyrene-tagged β-hydroxy acid and perylen-3-ylmethylmethacrylate co-N-dodecylmethacryl-amide polymer, compared to control, pyrene boronic ester. The quenching is due to dynamic quenching between the donor and acceptor. Furthermore, aggregation was not observed from the pyrene-tagged β-hydroxy acid ester donor as the concentration of the solution is increased up to 3000 ppm.

In this study, the growth of copper on porous diatom silica by electroless deposition method has been demonstrated for the first time. Raman peaks of copper (145, 213, and 640 cm−1) appeared in the copper-coated, Amphora sp. and Skeletonema sp. diatom samples, confirming the successful deposition of copper. Scanning electron microscopy (SEM) indicated the presence of copper on the diatom silica surface. The 3D intricate structure of diatom was still evident by optical and scanning electron microscopy analyses when the diatom samples were immersed in the copper bath for only 5 hours. Incubating the diatom samples in the copper bath for 24 h produced a dense coating on the diatom surface and covered the intricate 3D structure of the diatom silica. These results present possibilities of the fabrication of hierarchically organized copper with 3D diatom replica structures.

The simultaneous coupling and reduction of graphene oxide (GO) with diatom silica (Amphora sp., Navicula ramossisira and Skeletonema sp.) were demonstrated in this work. Binding of GO with diatom silica via direct esterification reaction at 100 °C was observed as well as the reduction of GO. The Raman spectra of GO-diatom silica revealed the typical peaks for reduced graphene oxide at 1350 cm−1 (D band) and 1585 cm−1 (G band). Infrared spectroscopy also showed the presence of a unique peak at 1260–1300 cm−1 indicative of Si–O–C=O bond formation. This confirms the successful functionalization of GO with silica. Scanning electron microscopy showed the presence of GO on the diatom. For the pennate diatoms, Amphora sp. and N. ramossisira, their pores were closed demonstrating that GO was able to cover the surface of the diatom via the Si–O–C bond formation. For the centric diatom, Skeletonema sp., GO was found to be on its rib cage-like body structure and on its centric top. Electrochemical measurements by cyclic voltammetry using a redox probe, K3[Fe(CN)6], showed that GO-Amphora and GO-Navicula had more surface negative charge compared with bare GO or bare diatom silica. Furthermore, they demonstrated similar surface charge characteristics as the chemically reduced GO (by hydrazine hydrate). This implies that the composite (reduced GO-diatom) can possibly replace chemically reduced GO (by exposure to hydrazine vapor) and it could probably function as an electrode in sensing cationic biomolecules.

In this study, enhancement in efficiency of anthocyanin-based dye sensitized solar cells (DSSC) through the incorporation of graphene directly into the dye mixture is demonstrated. Graphene was incorporated in the anthocyanin dye mixture and allowed to co-adsorb on the mesoporous titania; this is compared with anthocyanin-only mixture as control, and also compared with DSSC with graphene incorporated directly into the titania. Current–voltage (IV) and electrochemical impedance spectroscopy (EIS) measurements were carried out to characterize the different DSSC cells. Addition of graphene resulted in increased power conversion efficiencies: addition into the TiO2 as a photoanode composite, direct addition to the anthocyanin extracts (anthocyanin:graphene dispersion) during the adsorption step, or a combination of these two. The latter resulted in the highest enhancement in the PCE by as much as 2.4 times. EIS data showed a favorable decrease in charge transfer resistance in the TiO2 layer as graphene is added to the DSSC, with increased magnitude of the short-circuit current (Jsc). This is explained by graphene providing added conducting pathways for the photo-generated electrons; results show that this is also manifested in the co-adsorption of graphene with the anthocyanin dye onto the titania anode.

Enhanced photoelectrochemical (PEC) performances of Ga2O3 and GaN nanowires (NWs) grown in situ from GaN were demonstrated. The PEC conversion efficiencies of Ga2O3 and GaN NWs have been shown to be 0.906% and 1.09% respectively, in contrast to their 0.581% GaN thin film counterpart under similar experimental conditions. A low crystallinity buffer layer between the grown NWs and the substrate was found to be detrimental to the PEC performance, but the layer can be avoided at suitable growth conditions. A band bending at the surface of the GaN NWs generates an electric field that drives the photogenerated electrons and holes away from each other, preventing recombination, and was found to be responsible for the enhanced PEC performance. The enhanced PEC efficiency of the Ga2O3 NWs is aided by the optical absorption through a defect band centered 3.3 eV above the valence band of Ga2O3. These findings are believed to have opened up possibilities for enabling visible absorption, either by tailoring ion doping into wide bandgap Ga2O3 NWs, or by incorporation of indium to form InGaN NWs.